Did dithering change in latest update?


#1

I have noticed recently a sudden increase in dark pixel noise in my images. While looking at them using blink I noted that the dithering is barely dithering.

I even tried bumping it up to “Very high” dither but it still seems subdued.

At a focal length of 2,000 one would think it would be quite obvious!

I am pretty sure this started after I ‘finally’ ran an update to the latest version and wondered if something changed, or if there is some other setting I need to check.

Thanks.


#2

Hi @UlteriorModem

Interesting, I noticed the same thing. I found it to be strange but because of the very few clear nights we have had I didn’t think much about it since I didn’t have much to process. When I increased the dither in SGPro to “Very High” it didn’t seem to make much different. My FL is 1,960. Not sure if dithering is controlled in SGP or PHD2. I recently updated PHD2 to the latest development release v2.6.5.

I’m on the latest SGPro latest version but noticed this on the one version prior to this.

Mark


#3

Interisting, I haven’t updated my install of PHD2 in a while. When things are working I tend not to fix them :slight_smile:

I guess I will try extreme dither but you would think at these focal lengths it would be over kill.

I noted in phd2 there was a setting for ‘dither scale’ it was set at .8, 1.0 is the default so I will try adjusting that some and see what happens.

Thanks


#4

I am also seeing the same thing. Dithering was very easy to spot when moving from image to image in the prior version…not I am not entirely sure it is working at all in some frames…I can see movement in others but something has changed. I am using three different kits - One SCT and two Refractors and the dithering issue is consistent with all three.


#5

I’ve been noticing the same for a while. I’m imaging @ 1100 with an OAG. I’ve set the phd2 dither scale to 4 and now dithers appear to move significantly more than the guiding error.


#6

Doing some simulator testing it seems generally working OK. Are you at least seeing the dither notifications? Does the communication between SGP and PHD2 seem to be working correctly?

Thanks,
Jared


#7

Jared, Yes everything appears to be ‘working’ as it should, its just that the dither is very small considering I have “Very large” selected and a long focal length.

Last night I upped the scale in PHD form .8 to 1.25 but unfortunately clouds got the better of it and lost lock around 11pm and it never recovered from it. I had already went to bed.

Not related but also the log file shows a bunch of “Can pier flip now” errors…

[05/11/18 04:02:38.486][DEBUG] [CP Update Thread] Caught exception in CanPierFlipNow : Object reference not set to an instance of an object.
** at qr.k1()**

I assume that is because it was in parked position?

From the wopping 4 frames that I did get it appeared to dither more but not as much as might be expected.

I guess I will try larger scales in PHD and see what happens.

But I never had this issue before.


#8

Well as usual I have not had a chance to check out the dithering with the higher scale settings due to weather.

Stay tuned :slight_smile:


#9

Interesting, when I developed my M101 images posted this week, I could not detect the usual border misalignment after integration. There have been a couple of PHD2 snapshot releases this year and I will take more notice on my next session to determine if there is something amiss.


#10

Did the dither question ever get resolved? I’m seeing very little movement from image to image. I need to set the Dithering Option in SGP to “Extreme Dither”. My FL = 1960. Seems strange for such a long FL to need to set the Dithering to “Extreme”. Also in PHD2 i set the Dither to 1.5. I don’t recall this being an issue in previous version of SGP it only showed up in the 3.0 release.

Just thought I would ping this again to see what other folks have found and/or done to get more dithering.

Thanks,
Mark


#11

Believe it or not I have only one night to get out there since the initial observations. Sorry I had a tropical storm come through and knocked down the map. Also a trip to Chicago and… well yea one night.

Of course I forgot about this ‘minor’ issue and did not change a thing, but still after looking at the subframes I gathered that night there was ‘some’ dithering but not what you would expect for ‘high’ settings and a long focal length.

Next time I get out I will try to remember to change the settings.

I will also try to remember to report back with any conclusions :slight_smile:


#12

Dithering for me has also changed. I am using two wide-field systems too. The change from frame to frame is hardly noticeable - also using the “extreme dither” option.


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